Grinding wheel truing apparatus



June 22, 1948. c, YG 2,443,789

GRINDING WHEEL TRUING APPARATUS Filed March 29, 1947 3 Sheets-Sheet 1 Ill [war/r02 CHRL G. Fu/qmas -Qctan June 22, 1948. c. s. FLYGARE 2,443,789

GRINDING WHEEL TRUING APPARATUS Filed March 29, 1947 3 Sheets-Sheet 2 INVENTOR.

C0121; G FLYCi/QREZ BY W LO F7 TTOIEHEY June 22, 1948.

c. G. FLYGARE 2,443,789

GRINDING WHEEL TRUING APPARATUS Filed March 29, 1947 3 Sheets-Sheet 3 h @121 mpuii I INVEHTOB Cam. 6: Fzlmnze:

QTTOQHEY Patented June 22, 1948 2,443,789 Y GRINDING WHEEL TRUING APPARATUS Carl G. Flygare, Worcester, Mass., assignor to Norton Company, Worcester, Mass., at corporation of Massachusetts Application March 29, 1947, Serial No. 738,093

6 Claims. (Cl. 125-2) The invention relates to grinding machine and more particularly to a crush truing apparatus for truing a predetermined form on the peripheral or operative face of a grinding wheel.

One object of this invention is to provide a simple and thoroughly practical crush truing apparatus for truing a predetermined form on the operative face of a grinding wheel. Another object of the invention is to provide a crush truing apparatus in which the form crusher roll is moved hydraulically toward and away from the face of the wheel to be dressed. Another object of the invention is to provide a hydraulic control mechanism for a crush truing roll which is arranged to cause a rapid approaching movement of the crushing roll and automatically reducing the rapid approaching to a slow controlled feed as the crushing roll moves into operative engagement with the grinding wheel.

Another object of the invention is to provide a hydraulic mechanism for moving a crushing roll to and from an operative position in which a solenoid valve controls the direction of movement of the crusher roll and a second solenoid valve actuated automatically in timed relation with the movement of the crusher roll to reduce the rapid approaching to a controlled feedin movement. Another object of the invention is to provide a hydraulic piston and cylinder mechanism to control the movement of a crusher roll toward and from the operative face of a grinding wheel and to provide a booster piston and cylinder to increase the pressure of the crusher roll on the wheel during the crushing operation.

Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingl consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter escribed and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is shown one of various possible embodiments of the mechanical features of this invention:

Fig. 1 is a vertical sectional view through a wheel slide and the crush truing apparatus supported thereby, together with a hydraulic piping and electric wiring diagram;

Fig. 2 is a fragmentary plan view of the wheel slide, showing the grinding wheel driving mechanism;

Fig. 3 is a fragmentary sectional view, on an enlarged scale, taken approximately on the line 3-3 of Fig. 2, having parts broken away and iii 2 shown in section to illustrate the free-wheeling driving clutch;

Fig. 4 is a cross sectional view taken approximately on the line 44 of Fig. 3, through the free-wheeling clutch;

Fig. 5 is av fragmentary vertical sectional view through the manually operable feed mechanism for the crusher roll slide;

Fig. 6 is a modified form of the hydraulic actuating mechanism for the crusher roll and its supporting slide; and

Fig. '7 is a cross sectional view through a crusher roll.

A grinding machine has been illustrated in the drawings comprising a base Ill which supports a transversely movable wheel slide 15 on a transversely extending V-way l5 and a fiat way IT. The wheel slide is supports a rotatable wheel spindle la in a pair of spaced bearings l9 and 20. A grinding wheel 2| is mounted on the left hand end of the wheel spindle and a multi V-groove ulley 22 mounted on the right hand end thereof.

A suitable driving mechanism is provided for rotating the wheel spindle l8 and grinding wheel 2| at either a relatively fast speed for a grinding operation or at a relatively low speed for a crush truing operation. An electric motor 25 is mounted on the wheel slide IS. The motor 25 is provided with a motor shaft 26 which supports a multi V-groove pulley 21 which is connected, by multiple V-belts 28 with the pulley 22 on the wheel spindle Ill. The motor 25 and the belt drive above described serve to rotate the grinding wheel 2| at a normal grinding speed such as for example 5,000 surface feet per minute or more depending upon the nature of the work being ground and the type of grinding wheel being used.

A slow speed driving mechanism is provided to supplement the drivin mechanism above described for rotating the grindingwheel at a suitable speed for crush truing. This mechanism may comprise a relatively small electric motor 30 which is mounted adjacent to the rear portion of the wheel slide 15. The motor 30 is provided with a motor shaft 31 which supports a V-pulley 32. A V-belt 33 connects the pulley 32 with a V-pulley 34 on a speed reduction unit 35. The speed reduction unit 35 may be any of the standard well known speed reducing units which are available on the open market. This speed reduction unit may comprise a rotatable shaft 36 which supports the pulley 34. A worm 31 is either formed integral with or is fixedly mounted on the shaft 36. The worm 31 meshes with a worm gear 38 which is 'drivingly connected to rotate a shaft I 39. A free-wheeling clutch 48 is keyed to the shaft 39 and is provided with a V-groove pulley 4| which is connected by means of a single I-belt 42 with a pulley 43. The pulley 43 is mounted on the motor shaft 25.

g The free-wheeling clutch 48 (Figs. 3 and 4). comprises a sleeve 45 which is keyed to the shaft 39. The sleeve 45 supports a casing 48 on a pair of spaced ball bearings 41 and 48 (Fig. 4). Gear teeth 49 are formed on a flanged portion of the sleeve 45. A plurality of rocker cams 58, only one of which is shown in Fig. 3, are provided with gear teeth which mesh with the gear teeth 49 on the sleeve 45. When the motor 38 is set in motion, the sleeve 45 will be rotated in a clockwise direction as-shown by the. arrow in Fig. 3. This motion serves to rock the rocker cams 58 in a counter-clockwise direction so that the cam surface drivingly engages an internal cylindrical surface formed within the casing 45 so that the driving motion of the shaft 39 will be transmitted through the gear teeth 49. through the rocker cams 58 to frictionally engage the internal cylindrical surface 5| and thereby to rotate the casing 46 and the pulley 4| to transmit a rotary motion through the pulley 21, the belt 28, the pulley 22 to rotate-the wheel spindle I8 and the grinding wheel 2| at a relatively slow speed for a crush truing operation. This speed may be for example a peripheral speed of 150 to 300 surface feet per minute to produce the desired and predetermined truing operation. A plurality of springs 52 (Fig. 3) are provided normally to urge the rocker earns 58 in a clockwise direction so that when the motor 38 is idle and the motor 25 is in operation, the pulley 4| and the casing 46 is free to rotate during the normal grinding operation.

A vertically arranged truing apparatus frame is mounted on the upper portion of the wheel slide I5. The frame 55 serves as a support for a vertically movable slide 56 which is arranged to slide in slideways 51. The slide 56 serves as a support for a shaft 58. The shaft 58 supports a crusher type truing roll 59 on a pair of spaced anti-friction bearings 58 and 6|.

A coolant supply system is provided comprising a pipe 52 which is connected to a suitable source of supply of coolant fluid. The pipe 62 is connected to a housing 63 formed integral with or fixedly mounted on the slide 56. The housing 63 surrounds a portion of the crusher roll 59. A coolant nozzle 64 is mounted within the casing 53 to convey coolant fluid from the pipe 52 to the crusher roll 59 and the grinding wheel 2|.

A suitable feeding mechanism is provided for moving the crusher roll slide 56 either toward or from the grinding wheel 2|. This mechanism may comprise a vertically arranged feed screw 55 which is supported in a pair of spaced bearings 61 and 58. The bearings 61 and 58 are fixedly mounted relative to the truing apparatus frame 55. The slide 56 is provided with a threaded aperture or nut 59 which engages or meshes with the feed screw 55.

The feed screw 65 may be rotated manually to cause a relative approaching or receding movement of the slide 55 and the crusher roll 59 relative to the grinding wheel 2|. This mechanism may comprise a manually operable hand wheel 18 (Fig. 5). The hand wheel 18 is'mounted on one end of a rotatable shaft 1|. The shaft 1| is supported in anti-friction bearings 12 and 13 which are fixedly mounted relative to the frame 4 5 5. The shaft 1| supportsa bevel gear 14 on its inner end which meshes with a bevel gear 56 slidably keyed to the lower end of the feed screw shaft 55, It will be readily apparent from the foregoing disclosure that a rotary motion of the hand wheel 18 will be transmitted through the mechanism above described to cause a vertical movement of the slide 55 and the crusher roll 59.

It is desirable to provide a suitable power operated mechanism for rapidly moving the crusher roll to and from an operative position with the crusher roll 59 in trulng engagement with the periphery of the grinding wheel 2| and to maintain the crusher roll in engagement therewith at a predetermined relatively high pressure to produce the desired crushing action upon the perlphcry of the grinding wheel 2|. This mechanism is preferably a hydraulically operated mechanism comprising a cylinder 88 which contains a slidably mounted piston 8|. The piston BI is operatively connected to the upper end of the feed shaft 55. A solenoid control valve is provided for controlling the admission to and exhaust of fluid from the cylinder 88. This valve is preferably a piston type valve comprising a valve stem 83 having a plurality of valve pistons 84, 85 and 86 formed integral therewith. An electric solenoid 81 is provided which when energized serves to move the valve stem 83 upwardly so as to reverse the flow of fluid to the cylinder 88.

Electric power is supplied as represented by the power lines 88, These power lines 88 are connected so that when a switch 89 is closed, the solenoid 51 will be energized.

Fluid under pressure from any suitable source is supplied through a pipe 98 to a valve chamber 9| which is located between the valve pistons 85 and "5. In the position of the valve 82 as shown in Fig. 1, fluid under pressure entering the valve chamber 9| passes out through a pipe 92 and through a pipe 93 into a cylinder chamber 94 formed at the lower end of the cylinder 58. The admission of fluid under pressure to the cylinder chamber causes the piston 8| to move upwardly into the position illustrated in Fig. 1. During the upward movement of the piston 8|, fluid within a cylinder chamber 95 exhausts through a passage 95, through a pipe 91 into a valve chamber 98 located between the valve pistons 84 and and passes out through an exhaust pipe 99.

When the solenoid 81 is energized, fluid entering the valve chamber 9| from the pipe 98 passes through the pipe 91, through the passage into the cylinder chamber 95 to cause a downward movement of the piston 8|. During the down ward movement ofthe piston 8|, fluid within the cylinder chamber 94 is exhausted through the pipe 93, the pipe 92, into a valve chamber I88 and out through an exhaust pipe I8I.

In the preferred form of this invention, it is desirable to use a comparatively low pressure for example 100 pounds per square inch in the fluid pressure system so that during the approaching atively large diameter of the piston I09 as compared to the diameter of the piston rod I01, if 100 pounds per square inch pressure is applied above the piston I00, this pressure will be increased due to the difference in area of the piston I09 and the effective area of the piston rod I01. By this arrangement it is possible to maintain a relatively low line pressure a d at the same time to boost this pressure from, for example 100 pounds pressure per square inch in the supply line 90 so that an increase to 200 pounds per square inch or more is obtained within the booster cylinder 90.

A suitable control valve I09 is provided for controlling the admission of fluid to the booster cylinder I05. This control valve I09 is a piston type valve comprising a valve stem IIO having valve pistons III and H2 formed integrally therewith. In the position of the valve I09 (Fig. 1) fluid under pressure from the pipe 91 enters a valve chamber II3 formed between the valve pistons III and H2 and passes out through the passage 90 into the cylinder chamber 95 to cause a downward movement of the piston 9|. A compression spring Ill surrounding the valve stem IIO serve normally to maintain the valve I09 in the position illustrated in Fig. 1.

It is desirable to provide a suitable control mechanism so that the crusher roll 59 may be moved rapidly until it is about to engage the peripheral surface of the wheel 2| to be trued and then moved at a slower controlled rate during the crush truing of the grinding wheel 2 I. This is preferably accomplished by means of a solenoid valve I20. The solenoid valve I20 is a piston type valve comprising a valve stem I2I having formed integral therewith valve pistons I22 and I23. The valve I20 is interposed between the pipe lines 92 and 93. In the position of the valve as shown in Fig. 1, fluid under pressure passing through the pipe 92 enters a valve chamber I24 located between the valve pistons I22 and I23 and passes outwardly through the pipe 93 into the cylinder chamber 94 to cause an upward movement of the piston 8|, the slide 56 and the crusher roll 59.

When the solenoid 91 is energized to shift valve 82 upwardly to allow fluid to pass through the pipe 91 so as to cause a downward movement of the piston 9|, fluid within the cylinder chamber 94 exhausts through the pipe 93, the valve chamber I24, the pipe 92, the valve chamber I00 and out through the pipe IOI. This arrangement allows a substantial unrestricted exhaust of fluid from, the cylinder chamber, 94 so that the crusher roll moves at a comparatively rapid rate.

A compression spring I25 is provided normally to hold the valve stem I2I in a downward position as shown in Fig. 1. A solenoid I29 is provided which when energized serves to shift the valve stem I2I upwardly so that the valve piston I23 cuts off exhaust of fluid to the pipe 92. As the valve stem I2I moves upwardly, fluid exhausting through the pipe 93 into the valve chamber I24 may pass outwardly through a pipe and a throttle valve I21 into the pipe 92. By regulating the throttle valve I21, the rate of exhaust of iiruid from the cylinder chamber 94 may be readily controlled so as to obtain the desired feeding movement of the crusher roll 59 into the surface of the wheel being dressed.

It is desirable to provide a suitable automatic electrical control so that the solenoid I26 may be energized in timed relation with the downward movement of the crusher roll 59 so as to change from a rapid approaching movement to a slow controlled feed when the crusher roll 59 reaches a predetermined position. This is preferably accomplished by means of a normally open limit switch I34 which is mounted on the truing apparatus frame 55. A collar I35 is arranged in the path of an arm I35 which is supported by a rock shaft I31. The rock shaft I31 is supported in a suitable bearing formed in the frame 55. The rock shaft I31 also supports an arm I39 which carries an adjustably mounted screw I39. The screw I39 is arranged to move in the path of an actuating plunger I40 of the limit switch I34. It will be readily apparent from the foregoing disclosure that when the slide 56 moves downwardly, the. collar I35 will engage the arm I39 and rock the shaft I31, the arm I39 and the adjustably mounted screw I39 in a counter cloc wise direction to close the limit switch I34. When the limit switch I34 is closed, a circuit is closed thereby to energize the solenoid I26 so as to shift the valve stem I2I upwardly and thereby reduce the rapid approaching movement of the crusher roll 59 to a relatively slow controlled feeding movement. It will be readily apparent that by adjustment of the screw I39, the actuation of the plunger I40 and the closing of the limit switch I34 may be adjusted so that the rate of approaching movement of the crusher roll 59 relative to the periphery of the grinding wheel 2I may be reduced at the desired and predetermined interval.

A modified form of the hydraulic actuating mechanism for the crusher roll is shown in Fig. 6 in which the booster cylinder I05 and its controlling valve I09 is eliminated. With this arrangement a relatively high line pressure must be obtained in the hydraulic control system, for example 200 pounds per square inch or more in order to obtain the desired pressure of the crusher roll 59 against the periphery of the grinding wheel 2I during the crushing operation. In case this modified construction is utilized, the pipe 91 is connected to pass fluid directly into the cylinder chamber 95 to cause a downward movement thereof and the pipe 93 is connected directly with the lower cylinder chamber 94. With this modified arrangement, the control valves 92 and I20 are connected in the same manner as shown in Fig. 1.

After a truing operation has been completed, it is desirable to move the crusher roll rapidly in an upward direction to an inoperative position. In order to obtain this result, it is desirable that both the solenoid 81 and the solenoid I26 be deenergized at the same time. The electrical connections as illustrated in Fig. 1 are such that when the crushing operation has been completed, the switch 89 is opened thereby deenergizing both the solenoid 81 and the solenoid I25 so that fluid under pressure from the pipe 90 passing into the valve chamber 9| passes through the pipe 92, through the cylinder chamber I24 and the pipe 93 into the cylinder chamber 94 to cause a rapid upward movement of the piston 8| so as to impart a corresponding movement to the slide 59 and the crusher roll 59.

The crusher roll 59 as shown in Fig. 1 comprises a cylindrical surface having two fillets arranged at opposite ends thereof for truing a cylindrical face on the grinding wheel 2I having the corners thereof rounded to a predetermined radius. As shown in Fig. 7 a modified form of crusher roll I42 is illustrated whereby an irregular fomned face may be produced on the periphery of the grinding wheel being dressed. The shape of the crusher roll may be varied to producepractically any desirable shape or form on the periphery of the grinding wheel. It will be readily apparent from the disclosure contained herein that forms may be crush trued into the operative face of a grinding wheel by the crushing method which would be diflicult or impractical to form by use of a conventional type truing apparatus.

The operation of this improved crush truing apparatus will be readily apparent from the foregoing disclosure. A crusherroll59 is mounted in position on the spindle 58. The crusher roll 59 having a peripheral surface formed or shaped to produce the desired form or shape on the periphery of the grinding wheel 2|. When it is desired to true the grinding wheel 2|, the switch 89 is 'closed to allow fluid under pressure from the pipe 90 to pass through the system above described to cause a downward movement of the piston 8 I, the slide 56, and the crusher roll 59 at a rapid approaching rate. Assuming the booster cylinder arrangement of Fig. 1 is utilized and a relatively low pressure supplied in the pipe line 90, fluid under pressure passing through the pipe 91 enters the valve chamber I I 3, passes through the passage 96 into the cylinder chamber 95 to cause a downward movement of the piston 6|. This movement continues at a rapid rate until the solenoid I26 is energized, thus throttling the exhaust of fluid through the pipe 93. As soon as the solenoid I26 shifts the valve stem I2I, pressure within the cylinder chamber 95 builds up so that there is suflicient pressure in the valve chamber I I3 passing through a passage II5 into a valve chamber H6 at the lower end of the control valve I01 to raise the valve stem IIIl against the compression of the spring Ill so that fluid under pressure within the valve chamber H3 may pass through a passage III in the booster cylinder I05 thereby causing a downward movement of the booster piston I06 so that the piston rod I91 as above described will increase or boost the pressure within the chamber I08 and the cylinder chamber 95 during the crushing operation. The rapid approach of the crusher roll 59 continues until the collar I35 engages the arm I36 so as to rock the screw I39 to close the limit switch I34 thereby energizing the solenoid I26 to shift valve stem I2I and thereby throttle the exhaust of fluid from the pipe 93 to a predetermined crushing rate as thecrushing roll 59 moves into operative engagement with the peripheral surface of the grinding wheel 2|. The crushing operation continues until the surface of the wheel has been dressed to the desired extent after which the switch 89 is opened to simultaneously deenergize both the solenoid 81 and the solenoid I26 thus allowing an unrestricted flow of fluid to the cylinder chamber 94-to cause a rapid upward movement of the piston BI, the slide 56 and the crusher roll 59 to an inoperative position.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a grinding machine having a rotatable slow speed for a truing operation, and a truing apparatus including a rotatably mounted crusher roller, a movable slide to support said roller, a hydraulic piston and cylinder rapidly to move said slide and crusher roller toward and from the face of the grinding wheel to be trued, a control valve to control the admission to and exhaust of fluid from said cylinder, a second normally open control valve connected between the lower end of said cylinder and the first valve. a throttle valve to control the exhaust of fluid from the lower end of said cylinder after the second valve is closed, and means includinga limit switch actuated by and in timed relation with the approaching movement of the piston to actuate the second valve so as to change the rapid approaching movement of the crusher roller to a relatively slow'controlled feeding movement when the crusher roller moves into operative engagement with the grinding tate said grinding wheel either at a relatively fast speed for a. grinding operation or at a relatively slow speed for a truing operation, and a truing apparatus including a rotatably mounted formed crusher roller, a vertically movable slide to support said roller, a hydraulic piston and cylinder axially aligned with said screw rapidly to move said screw-slide and crusher roller toward and from the face of the grinding wheel to be trued, a solenoid valve to control the admission to and exhaust of fluid from said cylinder, a second normally open solenoid valve connected between the lower end of said cylinder and the first valve normally to facilitate a rapid approaching movement of the f ing movement of the crusher roller to a relatively slow controlled feeding movement when the crusher roller moves into operative engagementv with the grinding wheel.

3. In a. grinding machine having a rotatable grinding wheel, independent electric motors to rotate said grinding wheel either at a relatively fast speed for a grinding operation or at a relatively slow speed for a truing operation, and a truing apparatus including a rotatably mounted formed crusher roller, a vertically movable slide to support said roller, a manually operable nut and screw to facilitate adjustment of said slide, a hydraulic piston and cylinder axially aligned with said screw rapid-1y to move said screw-slide and crusher roller toward and from the face of the grinding wheel to be trued, a solenoid valve to control the admission to and exhaust of fluid from said cylinder, a second norm-ally open solenoid valve connected between the lower end of said cylinder and the first valve normally to facilitate a rapid approaching movement of thecrusher roller, a throttle valve to control the exhaust of fluid from the lower end of said cylinder after the second valve is closed, and a limit switch actuated by and in timed relation with the downward movement of the piston to energize said second solenoid valve to change the rapid approaching movement of the crusher roller to a relatively slow controlled feeding movement when the crusher roller moves into operative engagement with the grinding wheel.

4. In a grinding machine having a rotatable grinding wheel, driving means to rotate said grinding wheel either at a relatively fast speed for a grinding operation or at a relatively slow speed for a truing operation, and a truing apparatus including a rotatably mounted formed crusher roller, a movable slide to support said roller, a hydraulic piston and cylinder rapidly to move said slide and roller toward and from the periphery of the grinding wheel, a second piston and cylinder to increase the pressure on the first piston and slide, a. normally open solenoid valve in the exhaust side of the first cylinder, a limit switch actuated by and in timed relation with the approaching movement of the slide and crusher roller to shift said solenoid valve so as to cut-off unrestricted exhaust of fluid from said cylinder, and a throttle valve to regulate the exhaust of fluid from the first cylinder after the solenoid valve is shifted to controlthe rate of movement of the crusher roller during a crushing operation.

5. In a grinding machine having a rotatable grinding wheel, driving means to rotate said grinding wheel either at a relatively fast speed for a grinding operation or at relatively slow speed for a truing operation, and a truing apparatus including a rotatably mounted formed crusher roller, a vertically movable slide to support said roller, a manually operable nut and screw to facilitate adjustment of said slide, a hydraulic piston and cylinder axially aligned with said screw rapidly to move said screw-slide and roller toward and from the periphery 01' said grinding wheel, a second piston and cylinder to increase the downward pressure on the first piston and screw, a normally open solenoid valve in the exhaust side of the first cylinder, a limit switch actuated by and in timed relation with the downward movement of said screw automaticaily to shift said solenoid valve to cut-oil unrestricted exhaust of fluid from said cylinder, a

10 throttle valve to regulate the exhaust of fluid from the cylinder after the solenoid valve is shifted to control the rate of movement of the crusher roller toward the peripheral face of the grinding wheel, and a control valve automatically actuated by back pressure in the first cylinder so as to admit fluid under pressure to the second cylinder and thereby to increase the pressure of the crusher roller against the grinding wheel during a crushing operation.

6. In a grinding machine having a rotatable grinding wheel, driving means to rotate said grinding wheel either at a relatively fast speed for a grinding operation or at a relatively slow speed for a truing operation, and a truing apparatus therefor including a rotatably mounted formed crusher roller for truing a predetermined shape on said wheel, a vertically movable slide to support said crusher roller, a hydraulic piston and cylinder to move said slide toward and from said wheel periphery, a manually operable nut and screw interposed between said slide and said piston to facilitate adjustment of the slide relative to the piston, a solenoid control valve to control the admission to and exhaust of fluid from said cylinder, normally open solenoid valve in the pipe 'line between said control valve and the lower end of said cylinder, means including a limit switch actuated by and in time relation with the downward movement of said slide to close said second solenoid valve, a throttle valve to control the rate of the exhaust when the second solenoid valve is closed, a booster piston and cylinder which is arranged to increase the pressure in the upper cylinder chamber, and a normally closed control valve which is open by back pressure in the pipe line between the control valve and the upper end of said cylinder when the solenoid valve is closed to open said latter valve and admit fluid under pressure to the booster cylinder thereby to increase the pressure of crusher roller against grinding wheel during a truing operation.

CARL G. FLYGARE. 

